Time zones:Mountain — Entire length
NOTE: Arizona does not observe Daylight Saving Time. All of Interstate 19 in Arizona is on Mountain Standard Time (UTC–7:00) year round.

Counties traversed:Arizona — Santa Cruz, Pima

A quick hypertext drive: I-19 is signed largely in metric units; at one point, all signage was metric. Today, the highway features kilometer posts and exit signs that state the distance to the exit in kilometers; however, speed-limit signage uses conventional units (75 mph instead of 120 km/h).

I have received two descriptions of I-19 via e-mail; one is from Rich Piehl, a regular contributor to the USENET newsgroup misc.transport.road, and the other is from a person identifying himself/herself as “S.P. from Arizona.” Both of them mentioned I-19 being four lanes over its entire length, and that there are good views of a mountain range off to the west, particularly south of Tubac. “S.P.” also mentioned several other things: the White Dove of the Desert, an old mission located in the San Xavier Indian reservation just south of Tucson; the semi-permanent Border Patrol/INS checkpoints on the northbound side just north of Nogales; and the maquiladoras, or factories, located in the 12-mile-wide border commercial zone where Mexican vehicles can travel freely. The freeway itself comes to an end at a traffic signal one block north of the border itself; however, only cars can use this border crossing — trucks crossing into Mexico are instructed to use a separate border crossing roughly a mile to the west.